This application relates generally to the field of forward looking radar systems and, more particularly, to insuring proper physical alignment of forward looking radar systems on vehicles.
Forward looking radar systems are quite common now for vehicle features such as; adaptive cruise control, forward collision warning, and pre-crash braking. To ensure proper operation, the radar must be properly aligned to the vehicle's horizontal thrust direction, and must be aligned parallel with the road surface. In addition, the vehicle must be aligned properly in relation to the road. The common solution utilizes a radar module bracket that aligns the radar to the vehicle. Such brackets may have adjustment mechanisms and in-plant assembly and service procedures developed to align the radar.
More particularly, a forward looking radar module and bracket system is in production today on several car lines. The radar sensor is mounted to body structure behind the car's front fascia and “looks” forward down the road up to 150 meters or more. The module must be physically aligned horizontal to the ground (approximately +1 degree accuracy), and parallel to the vehicles thrust axis (approximately +1 degree accuracy). In this type of radar bracket system, alignment is controlled with a sophisticated, robust, and expensive bracket system designed to account for all vehicle build variations, and a post-build vehicle radar based target procedure is used to confirm proper alignment. With this type of bracket system, manual alignment changes are typically not performed online to maintain vehicle build throughput rates, although alignment service can occasionally be performed in an off-line environment if repair is required.
Multiple copies of the radar alignment system are required in the vehicle manufacturing process to provide adequate throughput cycle times. A primary failure mode of the radar based target alignment checking procedure is that the system can fail if the radar targets are not in the proper design position. Target misalignment can occur due to alignment mechanism wear or damage for example. An alternate radar alignment method, using a laser beam reflected from the module, is also difficult to implement and maintain. Additionally design considerations must be taken to allow for hitting the hidden module with an external laser beam, which is problematic and can have significant implications on vehicle styling and cost.
It would be desirable to have a method to allow the module to self-report its orientation, using gravity as a reference, and possibly the thrust axis information, if required. This method would allow the radar to diagnose without external equipment, and would provide an opportunity for continuous diagnostics, which is not possible with today's alignment system. It will be desirable, in addition, to establish an internal radar orientation measurement system would avoid the cost, labor, throughput impact, and failure modes of using external radar alignment equipment.
It would also be beneficial to develop an alignment method immune to vehicle changes, such as vehicle model and ride height, and positioning within the alignment stations.